George H.W. Bush died in his Houston home on Nov. 30, less than eight months after his wife of 73 years, Barbara. He was 94.

While Bush’s cause of death was not immediately known, a range of factors can cause spouses to die around the same time. A 2013 study published in the Journals ofGerontology found that the death of a spouse raises a person’s risk of dying by around 30%, compared to those who are still married. Some estimates are even higher. Some research has shown that in the six months after the death of a spouse, the bereaved face odds of mortality 40% to 70% greater than the general public, according to the American Psychological Association.

This phenomenon can likely be explained, at least in part, by common-sense factors; married couples tend to be around the same age and share many lifestyle habits, for example. In the Bushes’ case, George H.W. and Barbara were 17 and 16, respectively, when they met in 1941, and George H.W. was 94 when he died, while Barbara was 92. Their 73-year union made them the longest-married presidential couple ever.

Experts say the emotional devastation of losing a life partner can also take a toll, sometimes even causing a potentially deadly condition commonly known as broken-heart syndrome (or by its medical name, takotsubo cardiomyopathy).

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“The brain has a system in it to deal with acute, serious, life-threatening stress,” explains Dr. Martin Samuels, the chair of neurology at Brigham and Women’s Hospital in Boston and a broken-heart syndrome researcher. “[With broken-heart syndrome], the stress is so great that the chemicals affect the heart such that it fails to contract normally.” The heart assumes an abnormal shape, which leads to decreased blood flow to the coronary arteries and to the rest of the body, he says.

Broken-heart syndrome doesn’t necessarily strike right after a partner dies. Memories and dreams occurring in the weeks and months after a spouse’s death may be jarring enough to trigger the stress response, Samuels says. The condition has also been known to affect those who have lost a child (potentially including Debbie Reynolds, who died a day after her daughter, Carrie Fisher, in 2016), close friend or even a beloved pet.

Broken-heart syndrome is often reversible, Samuels says, but severe cases can cause sudden death. Even if broken-heart syndrome isn’t the cause of death, losing a loved one can trigger many other health issues due to an immune system compromised by stress, Samuels says. A 2014 study published in JAMA found that people who lost a spouse were more likely than non-grieving peers to suffer a heart attack or stroke in the next 30 days.

“Any organ can fail, or all the organs can fail,” Samuels says. “Losing a spouse is one of the most stressful circumstances that human beings have to face.”

Men may be particularly likely to suffer health consequences as a result of that upheaval. A 2013 study published in the journal Economics & Human Biology found that recently widowed men had 30% higher chances of dying, relative to their normal odds of mortality. The same wasn’t true for women who lost their husbands.

“Men often rely on their spouses for important sources of support and care, particularly at older ages,” says Matthew Dupre, an associate professor of population health sciences at the Duke University School of Medicine. (Dupre has researched the health impact of marriages ending, but was not involved in the Economics & Human Biology study.) “Beyond the immediate stress of losing a spouse, widowed men also lose a close companion that may encourage healthy eating, taking medications as prescribed and other healthful habits over the long run.”

Unfortunately, there isn’t much people can do to prepare their health for the impending loss of a spouse, Dupre says. At the very least, people should steel themselves for the reality of what’s to come, however far down the road.

“It’s important for older adults to understand how the loss of a significant loved one may impact their own health and longevity,” Dupre says. “It is also important for health care providers, family and others to be vigilant in providing those the support that is needed to cope with the death of a spouse — particularly among those who are facing their own health issues.”